1. Field of the Invention
The present invention relates generally to a direction indicator lamp flasher system adapted to flash direction indicator lamps of a vehicle. In particular, the present invention relates to an effective means for preventing a direction indicator flasher system from malfunctioning due to noise, and for preventing a direction indicator flasher system from malfunctioning due to so-called chattering signals, that might occur due to mechanical vibration of a movable contact piece during the turning ON of a contact of a relay or a turn-signal switch used for opening and closing an electrical circuit leading to the direction indicator lamps.
2. Description of the Related Art
A conventional direction indicator lamp flasher system is shown, for example, in Japanese Unexamined Patent Publication (Kokai) No. S61-166742. This conventional flasher system is configured by externally attaching a noise-absorbing capacitor to an integrated circuit, and connecting a flash-operation controlling circuit in an electrical circuit extending between a relay and a turn-signal switch, so that the operating states of the relay and the turn-signal switch are detected to control the operation of a flash-driving circuit.
However, with a prior art flasher system having a noise absorbing capacitor externally connected to the integrated circuit, as in the above-mentioned conventional art, the noise absorbing effect greatly varies depending on, for example, the mounting location of the noise absorbing capacitor and the shape of pattern traces formed on the printed circuit board on which the flasher system is assembled. This dependence of the noise absorbing effect on the mounting location of the noise absorbing capacitor and the shape of pattern traces necessitates repeated assembly attempts when designing the pattern traces of the circuit board. As a consequence, there has been a problem of necessitating many developing processes, thereby leading to much development work.
Moreover, a capacitor having a relatively large capacitance is required in some cases in order to increase the noise absorbing effect. In addition, when closing the contacts of the turn signal switch and relay that switches on and off the electrical path connecting to the direction indicator lamps, the mechanical vibration of the movable contacts results in chattering signals which in turn cause the system to malfunction.